JPH05201772A - Mixture and method for forming fire-resistant body combined to surface - Google Patents

Abstract

PURPOSE: To improve the bonding strength by projecting a mixture comprising compatible Si particles, at least one kind of refractory particles, specific particles and/or particles of another substance which particles are nonmetallic against the surface of a refractory simultaneously with oxygen.

CONSTITUTION: ≤70 Wt.% of one refractory particles such as SiC or SiO₂ whose grain diameter is less than 4 mm, ≤15 wt.% of combustible Si or Si and Al, particles with a grain diameter of less than 50 μm, and additive particles of a non-metal compound such as of MgO and/or peroxide with a grain diameter of 10-500 μm to cause introduction of SiO₂ produced by the combustion of Si particles into the crystalline lattice are blended in a way that the total amount of the additive is 25 wt.% or below to prepare the coherent refractory mass. Then the refractory forming mixture is projected to a surface of the refractory structure based on SiC or the like with a pure oxygen flow to be bonded with the substrate at ≤1000°C to obtain the refractory mass.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

The present invention provides a mixture of refractory particles and combustible particles which, under the action of heat of combustion, release sufficient heat to form the refractory body and react exothermically with projected oxygen. Is projected onto the surface simultaneously with oxygen to form a bonded refractory body on the surface. The present invention also provides a mixture of refractory particles with particles of a flammable substance capable of undergoing an exothermic reaction with oxygen to release sufficient heat to form the refractory body under the heat of combustion. It also relates to a particle mixture for the method of projecting onto a surface to form a bonded refractory body on the surface.

If it is desired to form a refractory body at a location on the surface, one of two well-known major methods can be selected.

Of these methods, British Patent No. 133089
In the first method, often referred to as "ceramic welding", which is exemplified in No. 4 (Gravel Bell) and British Patent No. 2170191 (Gravel Bell), flammable particles and refractory particles in the presence of oxygen The mixture is projected onto the surface to form a refractory body bonded to the surface.
Combustible particles and exothermic reaction with oxygen to form refractory oxides, and release the heat necessary to at least superficially melt the projected refractory particles, particles with composition and particle size measurement results That is. Examples of combustible substances of this type include aluminum and silicon. To be precise, it is well known that silicon should be classified as a semi-metal, but because silicon behaves similarly to certain metals (in forming refractory oxides, However, these combustible elements may be simply referred to as combustible metals. In general, it is recommended that the projection of particles be carried out in the presence of high-concentration oxygen, for example, by using commercially available oxygen as a gas carrier. In this way, bonded refractory bodies are formed and adhere to the surface onto which the particles have been projected. Since the temperature that can be reached by the ceramic welding reaction is extremely high, even if slag is generated on the surface of the refractory material to be treated, it can penetrate through it and soften and melt the surface, so the treated surface and the newly formed refractory Good coupling occurs between objects.

These well-known ceramic welding methods can be used for forming refractory articles such as blocks having a special shape, but most widely used for forming coatings or for repairing bricks and walls. Thus, it is particularly useful for repairing, reinforcing existing fire resistant structures, for repairing walls such as furnace walls in, for example, glass making furnaces, or coke ovens, or coating refractory equipment.

This operation is generally carried out when the temperature of the refractory substrate is high. As a result, it is possible to repair the erosion surface of the refractory, possibly while the equipment is in operation, while the equipment is maintained at substantially operating temperatures.

A second well-known method for forming refractory objects on surfaces is what is called the "flame spray method". The method directs a frame to a location where a refractory body is formed and sprays refractory powder across the frame. The flame can be supplied by gaseous or liquid fuel as well as coke powder. It is clear that the flame spray technique requires complete combustion of the fuel in order to generate the hottest flame possible and achieve maximum efficiency. Generally, the flame temperature achieved by flame spraying is not as high as that achievable with ceramic welding technology, so the resulting refractory body does not bond as well, and new refractory bodies and refractory substrates are not well bonded. The low bond formation temperature between the materials results in poor bond strength. Furthermore, the welding reaction is more suitable than the flame spray method for penetrating the slag that is likely to be generated on the treated surface of the refractory.

The composition of the mixture used in the ceramic welding process is generally selected to be similar to or similar to the chemical composition of the refractory material as the substrate, producing a repair object.
As a result, the compatibility and the adhesiveness between the new substance and the substance serving as a base material on which the new substance is formed are promoted.

However, when it is desired to repair a certain type of refractory structure, it has been observed that even when a refractory body having a chemical composition similar to that of the base refractory body is formed, some problems occur. There is.

For example, the surface of a refractory structure based on silicon carbide is repaired with a mixture mainly containing particles of carbon and silicon; and particles of metallic combustible material such as aluminum and silicon particles. However, the refractory body produced does not always show sufficient adhesion to the refractory body of the substrate.

Refractory materials with silicon carbide substrates are used in some metalworking equipment, especially in blast furnaces in the steel industry or in zinc distilling columns. During operation of the present apparatus, the minimum operating temperature of a portion of the refractory structure is rather low, for example, about 700 ° C., and further, the ambient temperature may be considerably changed. Refractory bodies formed in these parts of the refractory structure by known techniques do not always show sufficient adhesion to the substrate refractory body, and in some cases, especially on blocks, or on low temperature refractory walls. It has been observed that new refractory bodies are completely separated from the base refractory bodies during repairs and are separated during operation of the equipment.

This is also the case when repairing a high density silica based refractory structure used in a coke oven (which is so called to distinguish it from conventional low density silica refractories). Similar problems occur. That is, even if it is possible to form a refractory material having the same chemical composition as the refractory material of the base material, the new object does not always adhere sufficiently, and when the furnace is operated, the refractory material of the base material is immediately separated from It even happens.

[0012] For example, a mixture of an inert carrier gas; a flammable, oxidizable substance and refractory oxide particles is fed to a flame spray device, and high pressure oxygen draws in and accelerates the carrier gas / particle mixture. For example, one method for repairing the lining of a furnace is known from international patent application WO 90/03848 (Wilmet / Willard). Willard applies the method to repair refractory blocks / bricks in the tuyere line of a copper smelting converter and to repair silicon carbide tray columns. For example, a mixture containing 79% silicon carbide, 16.25% silicon, 4% aluminum, and 0.75% magnesium is projected into a silicon carbide tray column through a dual bench-yuri air-oxygen system.

However, the use of metallic magnesium powder in the present process is disadvantageous in that there is at least some uncertainty as to the composition of the refractory coating formed due to the relative volatility of metallic magnesium. is there.

One of the objects of the present invention is to solve these problems.

According to the present invention, a mixture containing combustible particles and refractory particles which exothermically reacts with the projected oxygen by releasing sufficient heat to form a refractory body under the action of combustion heat is treated with oxygen. At the same time, it relates to a method of forming a refractory body having a silicon compound bonded on the surface of the substrate by projecting it onto the surface, which is characterized in that the mixture is (i) flammable silicon particles; (ii) refractory particles of one or more substances as a major part of the weight of the mixture; and
(iiia) with the additive particles of another substance that causes the introduction of silica into the crystal lattice of the combustion of the silicon particles during the formation of the refractory body; and / or (iiib) the refractory body is formed. In the meanwhile, it contains additive particles of a non-metallic compound, which produce the other substances mentioned which cause the introduction of the silica particles into the crystal lattice of the silica produced by the combustion of the silicon particles.

The invention also provides, under the action of the heat of combustion, to release sufficient heat to form the refractory body described above,
Particles for a method of forming a bonded refractory body on a surface based on a silicon compound by projecting a mixture containing flammable particles and refractory particles that undergo an exothermic reaction with oxygen onto the surface together with oxygen. In relation to the mixture, characterized in that the mixture is (i) with combustible silicon particles;
i) refractory particles of one or more substances as a major part of the mixture weight; and (iiia) the introduction of silicon particles into the crystal lattice of the silica produced by the combustion of the silicon particles during the formation of the refractory body. And / or (iiib) the other of the above-mentioned substances that cause the introduction of silica particles resulting from the combustion of the silicon particles into the crystal lattice of the silica particles during the formation of the refractory body. And a non-metallic compound additive particle that produces a substance.

Such a mixture and method combine parts to form high quality refractory bodies for repairing silicon compound-based surfaces, such as furnace refractory structures. Useful for welding to. When the repaired surface undergoes repeated thermal fluctuations during the operation of the device and / or when repairing relatively low temperatures such as temperatures between 600 and 1000 ° C. (eg 700 ° C.) It is possible to obtain a refractory body that exhibits excellent adhesion to the refractory material, but it goes without saying that the invention can also be applied to surfaces at temperatures outside this range.

The refractory body formed in accordance with the present invention is such that at the interface between the surface and the formed refractory body, the starting mixture is completely free of substances that cause the introduction of silica produced by the combustion of silicon into the crystal lattice. It exhibits a different thermal expansion from the refractory material obtained when it is not included. The advantages gained by the present invention are due at least in part to this difference at the interface and that the refractory body obtained exhibits a thermal expansion at the interface that is well matched to that of the refractory body in question. It is believed that this is due to things.

The flammable silicon particles (i) may be used as the sole flammable material or they may be mixed with particles of a more flammable material such as aluminum. Therefore, it is preferable to further mix combustible aluminum particles in the mixture. Aluminum particles can be rapidly oxidized to give off a very large amount of heat to form the refractory oxide itself. Therefore, the conformity of this property promotes the formation of high quality refractory objects.

The silicon content of the mixture according to the invention is 15
It is preferably less than wt%. This is important to limit the amount of unreacted silicon that may remain in the refractory body that is formed. It has been found that the presence of unreacted silicon in the formed refractory body poses a risk of degrading the quality of the refractory body.

To obtain a uniform object, refractory particles (ii)
Is at least 70% by weight, most preferably at least 75% by weight.

Additive particles (iiia), and / or (iii
b) preferably constitutes the balance of the mixture, 2 of the mixture
It may be up to 5% by weight, preferably 5 to 15% by weight.

The average particle size of the flammable particles (i) used in this mixture is preferably 50 μm or less.

In order to facilitate the production of a regular powder jet, it is preferable that the refractory particles (ii) contain substantially no particles of 4 mm or more, most preferably 2.5 mm or more.

The particle size of the additive particles (iiia) and / or (iiib) used in the mixture is 500 μm or less,
Alternatively, it is preferably equal to this. If too large particles are used, there is a risk that these particles will not play an effective role. These particle sizes should be at least 1
It is preferably set to 0 μm. If too fine particles are used, there is a risk of volatilization during the reaction.

A variety of materials are suitable for inducing the introduction of silica produced by the combustion of silicon into the crystal lattice during the formation of refractory bodies.

The above-mentioned additive (iiia), which causes the introduction of the silica produced by the combustion of silicon into the crystal lattice, is preferably added to the mixture in the form of magnesia particles.

The presence of the compound in the mixture which is projected onto the surface of the refractory to be repaired ensures that the refractory body produced has the correct heat resistance.

Further addition of magnesia to the mixture enables the formation of refractory bodies in which at least some of the silica produced by the combustion of silicon has been introduced into the forsterite type crystal lattice. As a result, the refractory material produced will ensure that it has the correct heat resistance.

If the mixture contains aluminum and magnesia, at least a portion of the silica produced by the combustion of silicon is within the crystal lattice of the forsterite structure and / or crystals of the spinel structure. Refractory bodies can be formed that are introduced into the lattice and / or into the crystal lattice of the cordierite structure.

The presence of a cordierite-structured crystal lattice in the refractory body produced ensures that the body has superior thermal shock resistance. The presence of crystal lattices of forsterite and / or spinel structure has a favorable effect on the heat resistance of the refractory body produced.

Calcium oxide, or other oxides such as iron (II) oxide, can also be added to the silica produced by the combustion of silicon.
It can be used as an additive (iiia) which causes the introduction into the crystal lattice.

When a refractory body is formed, an additive substance or substances (iii) having a composition that generates a substance that causes the introduction of silica produced by the combustion of silicon into the crystal lattice.
Particle mixtures which additionally or alternatively contain b) can also be used. Peroxides such as calcium peroxide, nitrides, carbides can also be used.

Oxides such as calcium oxide,
For example, in the case of calcium oxide, it can be added in the form of wollastonite (wollastonite) (CaO.SiO ₂ ).

The present invention is particularly useful for repairing refractory materials containing silicon carbide substrates or refractory materials containing high density silica substrates. Therefore, it is preferable to carry out the ceramic welding using a mixture in which the major part of the weight contains silicon carbide or silica, respectively.

It goes without saying that the present invention can also be used to repair other types of refractory based on cicholine, other than the refractories mentioned above, such as ordinary silica bricks and silica-alumina bricks.

The material, or materials, that make up the major portion of the weight of the mixture may be adapted to the composition of the refractory material for repair purposes or may be another material. In the latter case, a refractory body can be formed which, unlike the properties of the refractory being repaired, ideally has improved properties such as improved wear resistance or improved refractory properties. ..

Next, the present invention will be illustrated in more detail with reference to Examples.

Example 1 A refractory body is formed on the wall of a zinc distillation column. This wall is composed of a brick having silicon carbide as a base material. By forming refractory oxides, a mixture of material particles oxidizable under heat, magnesia particles, and refractory particles is projected onto these bricks. The wall temperature is 800 ° C. Mix 60
Project into a pure oxygen stream at a rate of kg / h. The composition of the mixture is as follows. SiO ₂ 79% by weight Si 8% by weight Al 5% by weight MgO 8% by weight

The silicon particles have a diameter of less than 45 μm and a specific surface area between 2500 and 8000 cm ² / g. Aluminum particles have a diameter of 45 μm or less and a specific surface area of 35.
It is between 00 and 6000 cm ² / g. The diameter of the silicon carbide particles is 1.47 mm or less, 60% by weight in the range of 1-1.47 mm, 20% in 0.5-1 mm, 0.125 m.
m or less is 20%. The average diameter of MgO particles is about 30
It is 0 μm. As used herein, the "average diameter" is the dimension such that 50% by weight of the particles have a diameter smaller than this average value.

It has been observed that the new refractory body is permanently adhered to the support even though the walls repaired by the method are subject to considerable variations in ambient temperature.

The structure of the produced object is examined under a microscope. A superior continuity is then observed between the new refractory body and the substrate refractory body. Also, the introduction of silica produced by the combustion of silicon into the crystal lattice of forsterite, cordierite, and aluminum spinel is observed.

For comparison purposes, the magnesia-free mixture was projected under the same conditions. The composition of this mixture is as follows. SiC 87 wt% Si 12 wt% Al 1 wt%

If the operation of the zinc distillation column is continued,
It is observed that the refractory material that formed quickly separates from the wall and becomes a solid block away.

This example is modified to use this mixture for repairing the bottom of a coke oven formed of normal silica bricks and silica-alumina bricks. It can adhere well to walls and undergo repairing objects with excellent wear resistance even when subjected to significant heat fluctuations.

Example 2 As a modification of Example 1, a mixture with the following composition is used: SiC 82 wt% Si 8 wt% Al 5 wt% MgO 5 wt%

The repair wall is made of silicon carbide based brick and has a temperature of 700.degree.

The refractory body obtained also adheres permanently to the wall.

Example 3 The purpose is to form a refractory body on the wall of a coke oven made of high density silica brick. Conventional silica bricks have an apparent density of about 1.80, whereas high-density bricks have an apparent density of about 1.89. Such bricks have recently emerged in the refractory market and have significantly advantageous properties with respect to gas permeability and thermal conductivity of bricks when compared to conventional silica bricks.

Repair is carried out on a wall with a temperature of about 750 ° C. with the following mixture: SiO ₂ 80.5% by weight Si 11.1% by weight Al 1% by weight MgO 7.4% by weight

The size of the SiO ₂ particles is 2 mm or less and 1
The range of up to 2 mm is 30% by weight at the maximum, and the range of 100 μm or less is 15% by weight or less.

The produced object adheres permanently to the wall.

On the other hand, if a similar mixture, but without magnesia, is projected under the same operating conditions and the wall is subjected to the various thermal conditions present during the operation of the furnace, the wall A refractory object is created that easily separates from.

Example 4 A refractory material based on a silicon compound, the purpose of which is to form a refractory body on the wall of a coke oven which does not exceed 900 ° C. but undergoes considerable fluctuations in ambient temperature. Is. The repair is carried out on a wall at a temperature of about 750 ° C. with a mixture of the following composition: SiO ₂ 80 wt% CaO ・ SiO ₂ (wollastonite) 8 wt% Si 8 wt% Al 4 wt%

The average diameter of wollastonite particles is about 30.
It is 0 μm. The size of the metal particles is as described in Example 1, and the size of the silica particles is as described in Example 3.

Claims (18)

[Claims] 1. A mixture containing flammable particles and refractory particles that exothermically reacts with the projected oxygen by releasing sufficient heat to form a refractory body under the action of combustion heat, simultaneously with oxygen. In a method of forming a refractory body bound to a silicon compound-based surface by projecting onto the surface, the mixture comprising: (i) flammable silicon particles; (ii) as a major portion of the weight of the mixture, Refractory particles of one or more substances; and (iiia) additive particles of other substances that, during the formation of the refractory body, cause the introduction of silica into the crystal lattice of the silica produced by the combustion of the silicon particles, and (Or) (iiib) contains additive particles of a non-metallic compound which, during the formation of the refractory body, produce the other substances mentioned above which cause the introduction of silica into the crystal lattice of the silica particles produced by the combustion of the silicon particles. Characterized by Method. 2. The substance (iiia) which causes the introduction of silica into the crystal lattice produced by the combustion of silicon particles.
The method for forming a refractory body according to claim 1, characterized in that is added to the mixture in the form of magnesia particles. 3. The method for forming a refractory body according to claim 2, wherein at least a part of silica produced by combustion of silicon is introduced into a crystal lattice of a forsterite structure. 4. The method for forming a refractory body according to claim 1, wherein the combustible particles (i) further contain aluminum particles. 5. At least a part of silica produced by combustion of silicon is introduced into a crystal lattice of a forsterite structure and / or a crystal lattice of a spinel structure and / or a crystal lattice of a cordierite structure. The method for forming a refractory body according to claim 2 or 4, characterized in that. 6. A method for forming a refractory body according to any of the preceding claims, characterized in that the non-metallic compound (iiib) is added to the mixture in the form of peroxide or silicate particles. 7. Formation of a refractory body according to claim 1, characterized in that the refractory particles (ii) constituting the main part of the mixture weight are silicon carbide particles. Method. 8. The method for forming a refractory body according to claim 1, wherein the refractory particles (ii) constituting the main part of the weight of the mixture are silica particles. .. 9. The method according to claim 1, wherein the surface temperature is 1000 ° C. or lower. 10. A mixture of flammable particles capable of undergoing an exothermic reaction with oxygen and refractory particles to release sufficient heat to form the refractory body under the action of combustion heat. In a particle mixture for a method of forming a refractory body bound to a silicon-based surface by projecting it onto a surface of oxygen, the mixture comprising: (i) flammable silicon particles; and (ii) the weight of the mixture. With refractory particles of one or more substances as a major part of; and (iiia) during the formation of refractory bodies, other that cause the introduction of silica into the crystalline lattice of the silica produced by the combustion of the silicon particles. Non-metallic, producing additive particles of substances and / or (iiib), during the formation of the refractory body, other substances mentioned above which cause the introduction of silica into the crystal lattice of the silica produced by the combustion of silicon particles. Contains additive particles of the compound Mixture characterized. 11. The mixture comprises the particles (i) of another substance.
Mixture according to claim 10, characterized in that it contains magnesia particles as iia). 12. The non-metallic compound (iii)
Mixture according to claim 10 or 11, characterized in that it contains particles of peroxide or silicate as b). 13. The flammable particles (i) further contain aluminum particles.
A mixture according to one of the: 14. A mixture according to claim 10, characterized in that the refractory particles (ii) constituting the major part of the mixture weight are silicon carbide particles. 15. Mixture according to one of claims 10 to 13, characterized in that the refractory particles (ii) constituting the major part of the mixture weight are silica particles. 16. The additive particles (iiia) or (iiib)
Mixture according to one of claims 10 to 15, characterized in that its particle size is less than or equal to 500 μm. 17. Mixture according to any one of claims 10 to 16, characterized in that the additive particles (iiia) or (iiib) have a particle size of at least 10 μm. 18. Mixture according to claim 10, characterized in that the silicon level contained is less than 15% by weight.